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Catalytic Application of Carbon-based Nanostructured Materials on Hydrogen Sorption Behavior of Light Metal Hydrides
(wiley, 2013) Rohit R. Shahi; O.N. Srivastava
The development of hydrogen storage materials with favorable thermodynamics (e.g., kinetics, desorption/adsorption temperature) has attracted considerable attention in recent years. Alanates, amide-hydride mixtures and magnesium hydride are the candidates with the most potential storage material due to their high hydrogen storage capacity and good reversibility, but each has its own limitations (e.g., high desorption temperature and sluggish kinetics). Carbon has many allotropes such as graphite, activated carbon, fullerenes, carbon nanotubes, and the most recent, graphene, etc. These have novel properties which are useful in many new innovative applications. Several recent investigations have also demonstrated the benefi cial effect of carbon materials as catalyst for enhancing sorption behavior of different light hydrogen storage materials. Carbon with a small curvature radius exhibits prominent "catalytic" effect for light metal and complex hydrides. The reduction in curvature radius of carbon nanostructures enhances the electron affi nity and interaction of carbon with hydrogen because the hydrogen release/combination energy has been changed, and consequently, the de-/rehydrogenation kinetics of the material is improved. In this chapter, we will highlight the current advances (including our recent works) in the hydrogen sorption enhancement of metal and complex hydrides by incorporating carbon nanomaterials as a catalyst. There will be a particular emphasis on carbon nanotubes, carbon nanofi bers and graphene employed as a catalyst for the aforesaid hydrogen storage materials. © 2014 Scrivener Publishing LLC. All rights reserved.
Synthesis of nano-carbon (nanotubes, nanofibres, graphene) materials
(Indian Academy of Sciences, 2011) Kalpana Awasthi; Rajesh Kumar; Himanshu Raghubanshi; Seema Awasthi; Ratnesh Pandey; Devinder Singh; T.P. Yadav; O.N. Srivastava
In the present study, we report the synthesis of carbon nanotubes (CNTs) using a new natural precursor: castor oil. The CNTs were synthesized by spray pyrolysis of castor oil-ferrocene solution at 850°C under an Ar atmosphere. We also report the synthesis of carbon nitrogen (C-N) nanotubes using castor oil- ferrocene-ammonia precursor. The as-grown CNTs and C-N nanotubes were characterized through scanning and transmission electron microscopic techniques. Graphitic nanofibres (GNFs) were synthesized by thermal decomposition of acetylene (C2H2) gas using Ni catalyst at 600°C. As-grown GNFs reveal both planar and helical morphology. We have investigated the structural and electrical properties of multi-walled CNTs (MWNTs)-polymer (polyacrylamide (PAM)) composites. The MWNTs-PAM composites were prepared using as purified, with ball milling and functionalized MWNTs by solution cast technique and characterized through SEM. A comparative study has been made on the electrical property of these MWNTs-PAM composites with different MWNTs loadings. It is shown that the ball milling and functionalization of MWNTs improves the dispersion of MWNTs into the polymer matrix. Enhanced electrical conductivity was observed for the MWNTs-PAM composites. Graphene samples were prepared by thermal exfoliation of graphite oxide. XRD analysis confirms the formation of graphene. © Indian Academy of Sciences.
Deployment of new carbon nanostructure: Graphene for drug delivery and biomedical applications
(Springer Verlag, 2016) Mahe Talat; O.N. Srivastava
Graphene, the well awarded and popularly known as 2D carbon allotrope, is a versatile material. Its unique physico-chemical properties finds its application in a wide range of areas ranging from quantum physics, nanoelectronics, energy research, catalysis and engineering of nanocomposites, biomaterials and drug delivery. In principle, it is possible to produce graphene from high purity graphite sheet. Since graphite is stacked layers of many graphene sheets, bonded together by week van der Waals force and if these forces are disrupted individual graphene sheets can be separated out. In the present chapter we will discuss different methods of the synthesis of graphene like LPCVD, CVD (Chemical Vapor Deposition), thermal exfoliation, arc discharge, electrochemical exfoliation and chemical reduction. Since graphene having an innate property of hydrophobicity have the tendency to agglomeration and insolubility. To overcome the aforementioned insolubility some functionality needs to be attached to the graphene sheet. Therefore, different methods of functionalization like covalent and non-covalent approaches are also discussed. The last part of the chapter will deal with the application of graphene particularly in the drug delivery and biomedical field. © Springer India 2016.
Studies on the dispersion of carbon nanotubes and graphene in aqueous solutions with different types of surfactants
(American Scientific Publishers, 2014) Mahe Talat; Kalpana Awasthi; O.N. Srivastava
In this work, the dispersion of graphene and carbon nanotubes (CNTs) in aqueous solutions using various kinds of surfactants was studied. The graphene was synthesized from thermal exfoliation of graphite by slightly modified Staudenmaier method, whereas CNTs were synthesized by well known chemical vapor deposition method. The resultant carbon nanostructures were dispersed in water solutions of surfactants of different types like anionic (SDS), cationic (CTAB) and non-ionic (PEG) and by ultrasonication. The as-prepared and surfactant bearing carbon nanostructures were characterized by scanning and transmission electron microscopy and Raman spectroscopy. The rate of sedimentation of carbon nanostructures suspension was also observed. Some examples of use of these surfactant bearing carbon nanostructures for the attachment of biomolecules (e.g., DNA, BSA) are also presented. © 2014 American Scientific Publishers. All rights reserved.
Formation of single-walled carbon nanotube buckybooks, graphene nanosheets and metal decorated graphene
(Trans Tech Publications Ltd, 2018) Seema Awasthi; Kalpana Awasthi; O.N. Srivastava
The present study deals with the systematic study of the synthesis of various useful carbon nanostructures e.g. single-walled carbon nanotubes (SWCNTs) and graphene in large quantity by electrical arc discharge method by only varying the argon atmosphere pressure. The as-synthesized nanostructures were characterized by different characterization techniques such as XRD, SEM, TEM, Energy dispersive X-ray spectroscopy, Raman and FTIR spectroscopy. The SWCNT webs of length ~6 cm abundantly containing aligned SWCNTs have diameter of about 1.8 nm and form buckybook like structure. Few layer graphene (FLG) sheets were prepared by electric arc discharge of high purity graphite electrodes in a varying argon gas atmosphere (250 -500T). The largest areal extent of graphene (with lowest number of layer i.e. four) has been found at 350T argon pressure. A one step method is reported for the decoration of the graphene nanosheets with iron and nickel nanoparticles through arc discharge method. © 2018 Trans Tech Publications, Switzerland.
Formation of single and multi-walled carbon nanotubes and graphene from Indian bituminous coal
(Elsevier Ltd, 2015) Seema Awasthi; Kalpana Awasthi; A.K. Ghosh; S.K. Srivastava; O.N. Srivastava
Single-walled carbon nanotubes (SWCNTs) have been synthesized by electric arc discharge method using annealed coal electrode in the presence of Fe as well as Ni-Y as catalysts. Multi-walled carbon nanotubes (MWCNTs) have been synthesized without using any catalysts. The efforts have also been made to synthesized graphene like nanosheets from bituminous coal. The as-synthesized samples have been characterized through scanning and transmission electron microscopy, Raman and Fourier transform infrared spectroscopy. The formation of SWCNTs which holds nearly perfect one dimensional structure is confirmed by the presence of radial breathing mode. A feasible mechanism of CNTs formation from coal described here with the help of Fourier transform infrared spectroscopy. © 2015 Elsevier Ltd. All rights reserved.
Synthesis of reduced graphene oxide-TiO2 nanoparticle composite systems and its application in hydrogen production
(Elsevier Ltd, 2014) Pawan Kumar Dubey; Prashant Tripathi; R.S. Tiwari; A.S.K. Sinha; O.N. Srivastava
The utilization of solar energy for the conversion of water to hydrogen and oxygen has been considered to be an efficient strategy to solve crisis of energy and environment. Here, we report the synthesis of reduced graphene oxide-TiO2 nanoparticle composite system through the photocatalytic reduction of graphite oxide using TiO2 nanoparticles. Photoelectrochemical characterizations and hydrogen evolution measurements of these nanocomposites reveal that the presence of graphene enhances the photocurrent density and hydrogen generation rate. The optimum photocurrent density and hydrogen generation rate has been found to be 3.4 mA cm-2 and 127.5 μmole cm-2h-1 in 0.5 M Na2SO4 electrolyte solution under 1.5AM solar irradiance of white light with illumination intensity of 100 mW cm-2. In graphene-TiO2 nanocomposite, photogenerated electrons in TiO2 are scavenged by graphene sheets and percolate to counter electrode to reduce H+ to molecular hydrogen thus increasing the performance of water-splitting reaction. © 2014 Hydrogen Energy Publications, LLC.
Synthesis and characterizations of graphene/Sm doped BiFeO3 composites photoanode for efficient photo-electrochemical water splitting
(Elsevier Ltd, 2021) Alok K. Vishwakarma; Misba Hussain; Satish K. Verma; Vivek Shukla; M.A. Shaz; O.N. Srivastava
The present study features Bi1-xSmxFeO3 (BSFO) nanoparticles anchored on high-quality, reduced graphene oxide (RGO) sheets via a two-step ultrasonication method for photo-electrochemical (PEC) studies relating to solar hydrogen generation. Sm doping leads to the formation of pure BFO type phase without any secondary phases. The structural, morphological, optical, and local structure analyses of BSFO and BSFO@RGO have been done through X-ray diffraction, scanning electron microscope, UV–Vis spectrophotometer, and Raman spectrometer, respectively. The BSFO nanoparticles have been templated on reduced graphene oxide. The BSFO@RGO has been employed as a photoanode for PEC measurements under the simulated solar irradiation of intensity 100 mW-cm−1. The optimum photoanode has been found with Bi0.95S0.05FO3@RGO. The highest photocurrent density and solar to hydrogen (STH) conversion efficiency have been found as 2.40 mA/cm2 (at 0.5 V vs. saturated calomel electrode) and 2.45%, respectively. Furthermore, the stability of the photoanode against photo corrosion has also been tested by the chronoamperometric technique. During 2 h experiment, the average photocurrent density has been maintained at 1.5 mA/cm2 (at 0 V vs. SCE). The improved photocatalytic activity of BSFO@RGO has been explained based on the effect of doping, better solar spectral response, hindering the recombination loss of photo-generated charge carriers, and fast, facile charge transport. Although earlier studies have used Bi(Sm)FeO3 photoanode, hydrogen production has been observed for the first time in the present investigation to the best of our knowledge. Also, it appears that hydrogen production at zero external bias as observed in the present study suggests a new feature for bandgap tailored BFO. © 2021
Enhanced hydrogen generation by water electrolysis employing carbon nano-structure composites
(Elsevier Ltd, 2018) C.R.P. Patel; Prashant Tripathi; Alok K. Vishwakarma; M. Talat; Pawan K. Soni; T.P. Yadav; O.N. Srivastava
The present study describes the hydrogen generation through electrolysis by using graphene-carbon nanotube (GC) nano-composite electrode. Synthesis of GC nano-composites of various compositions utilizing solution admixing approach has been done. Structural, morphological, microstructural and analysis of quality of various carbon nano-composites have been investigated by using XRD, SEM, TEM, Raman and FTIR techniques. To determine the electrochemical catalytic performance of GC composites, these have been used as working electrode (anode) for electrolysis of water in an alkaline medium (1 M NaOH). The results reveal that the GC73 (70 wt% graphene and 30 wt% CNT) nano-composite is an optimum anode material for hydrogen production. The highest hydrogen production rate of 487 l/h-m2 has been observed for the composite GC 73. Based on Tafel plot and FTIR characterizations, a feasible mechanism for this high hydrogen yield has been put forward. © 2018 Hydrogen Energy Publications LLC
Synthesis, Characterization and Functionalization of Carbon Nanotubes and Graphene: A Glimpse of Their Application
(wiley, 2013) Mahe Talat; O.N. Srivastava
Since the discovery of nanomaterials, carbon nanotubes structures have attracted great interest in most areas of science and engineering due to their unique physical and chemical properties and are supposed to be a key component of nanotechnology. The most recent addition to the family of carbon nanostructures is graphene. Graphene is a one-atom-thick material consisting of sp2-bonded carbon with a honeycomb structure. It resembles a large polyaromatic molecule of semi-infi nite size. In the past fi ve years, graphene-based nanomaterials have been the focus of not only material scientists but also engineers and medical scientists. The interesting and exciting properties of single-layer graphene sheets have excited the scientifi c community especially in the areas of materials, physics, chemistry and medical science. The state-of-the-art CNT production encompasses numerous methods and new routes are continuously being developed. The most common synthesis techniques are arc discharge, laser ablation, high pressure carbon monoxide (HiPCO) and chemical vapor deposition (CVD) with many variants. Most of these processes take place in vacuum or with process gases. By choosing appropriate experimental parameters, large quantities of nanotubes can be synthesized by these methods. It is possible to control some properties of the fi nal product, such as type of CNTs synthesized (MWNTs vs. SWNTs), the quality of the nanotubes, the amount and type of impurities, and some structural CNT features. In this chapter we discuss some of the methods employed in our lab for the synthesis and characterization of the CNTs and graphene. For application in biomedical and targeted drug delivery, the major limitation of these nanomaterials is their poor solubility, agglomeration and processibility. Functionalization of CNTs and GS is, therefore, necessary to attach any desired compounds including drug and also to enhance the solubility and biocompatibility of these nanomaterials. Two types of functionalization methods, i.e., covalent and non-covalent methods are generally being adopted. We deliberate these two procedures of functionalization of CNTs and GS. The merits of these two modes of functionalization will also be discussed. © 2014 Scrivener Publishing LLC. All rights reserved.

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